EXCHANGE 


THE  PHYSICAL  ACTION  OF  LIME 
ON  CLAY  SOILS 


A  THESIS 

PRESENTED  TO  THE  FACULTY  OF  THE  GRADUATE  SCHOOL 
OF  CORNELL  UNIVERSITY  FOR  THE  DEGREE  OF 

DOCTOR  OF  PHILOSOPHY 


BY 
ROBERT  MIFFL1N  SNYDER 


December,  1917 


THE  PHYSICAL  ACTION  OF  LIME 
ON  CLAY  SOILS 


A  THESIS 

PRESENTED  TO  THE  FACULTY  OF  THE  GRADUATE  SCHOOL 
OF  CORNELL  UNIVERSITY  FOR  THE  DEGREE  OF 

DOCTOR  OF  PHILOSOPHY 


BY 
ROBERT  MIFFLIN  SNYDER 


December,  1917 


( 


EXCHANGE 


THE  PHYSICAL  ACTION  OF  LIME  ON  CLAY  SOILS 

The  recent  investigations  in  the  field  of  soil  acidity  have  raised  anew 
the  question  of  the  physical  action  of  lime  on  the  soil.  A  number  of 
physical  investigations  have  been  conducted  in  the  past,  but  the  recent 
progress  in  certain  auxiliary  subjects,  as  colloid  chemistry,  has  tended 
to  depreciate  the  value  of  much  of  this  work,  and  bring  new  problems 
to  the  front.  The  question  may  therefore  be  properly  considered  again : 
What  is  the  specific  effect  of  each  form  of  lime  on  the  soil,  and  how  great 
is  that  effect? 

Our  problem  resolves  itself  into  two  parts:  First,  the  selection  of 
desirable  methods,  and  second,  their  application.  Let  us  first  review  the 
procedures  available  for  the  study  of  the  colloidal  characteristics  of  the 
.soil,  and  determine  wherein  their  merits  and  deficiencies  lie.  The  vari- 
ous methods  may  be  classified  under  eight  distinct  headings,  as  follows: 

Methods  for  Estimating  Soil  Colloidality 

Flocculation  in  solution. 

1.  The  suspension  method. 
Solubility  of  colloidal  material. 

2.  Fraps  Ammonia  Method. 

3.  Van  Bemmelen  Acid  Method. 

4.  Endosmometer  method. 
Heat  Liberation  on  Wetting. 

.").     Poiiillet-Mitscherlich  Method. 
Capillarity  and  Eetentive  Power. 

6.  Hilgard  Total  Retentive  Cup  Method. 

7.  Briggs  and  McLane  Moisture  Equivalent  Method. 

8.  Capillary  Kise  of  Water. 

9.  Percolation  of  Water. 

10.  Atterberg  Plasticity  Method. 
Adsorption. 

11.  Hygroscopic  Water. 

12.  Dye  Adsorption. 

13.  Selective  Adsorption  of  ions. 

14.  Endell  Histological  Method. 
Volume  Change. 

15.  Expansion  Method. 

ACKNOWLEDGMENT 

The  writ'  r  takes  pleasure  in  ackiHovledging  his  obligations  to  Professors  T.  L.  Lyon.  W.  1). 
Bancroft.  T.  I*.  Briggs.  and  II.  O.  Buokman  for  helpful  criticisms  and  suggestions  He  is 
particularly  ;ndebted  to  Professor  J.  A.  Biz/oil,  under  The  immediate  di  ection  of  whom  the 

work    was   conducted. 


4  THE     PHYSICAL    ACTION    OF     LIME     ON     CLAY     SOILS 

Penetrability. 

16.  Penetration  Method   (Laboratory). 

17.  Dynamometer  Method  (Field). 
Oxidation. 

18.  The  Oxidation  Method. 

1.  The  Suspension  Method  has  been  used  more  extensively  than  any 
other.    It  consists  essentially  in  making  a  suspension  of  the  material  in 
the  particular  solution  to  be  tested,  and  observing  the  time  required  for 
precipitation.    For  a  number  of  decades  the  suspension  method  was  the 
only  means  by  which  the  effect  of  ions  on  the  stability  of  colloidal  ma- 
terial could  be  determined.     In  the  hands  of  Schulze,  Bams,  Picton  and 
Limler,  Bodlander,  and  Hardy,  it  was  of  immense  assistance  in  the  form 
ulation  of  the  fundamentals  of  colloid  chemistry.     The  specific  action  of 
various  salts,  and  the  valence  and  mass  relations,  have  been  popular  sub- 
jects for  study.     The  most   recent  work  with  clay  suspensions  has  been 
performed  by  Masoni,  and  by   \VolkotT. 

Valuable  as  the  suspension  procedure  has  been  in  the  preliminary 
studies,  the  question  nevertheless  arises  whether  it  should  be  considered 
a  legitimate  method  for  correctly  estimating  the  physical  effects  of  salts 
on  soils.  The  writer  is  of  the  opinion  that  the  precipitation  of  a  sol  by 
an  electrolyte  is  of  little  value  in  gauging  the  action  of  the  same  salt 
applied  to  a  soil  under  natural  conditions.  In  a  suspension  the  forces 
inhibiting  the  neutralization  of  charges  are  very  small,  while  in  a  heavy 
soil  the  internal  friction  prevents  the  formation  of  the  large  floccules 
characteristic  of  the  suspension.  Probably  in  many  heavy  clays  the  posi- 
tively changed  colloidal  iron  remains  indefinitely  in  approximate  con- 
tiguity to  the  negative  silicia  without  neutralization  taking  place. 

A  somewhat  similar  view  regarding  the  inapplicability  of  the  suspen- 
sion method  is  held  by  Free.  He  thinks  that  in  the  soil,  the  tension  at 
the  liquid-vapor  surface  may  be  the  determining  factor  in  precipitation. 

2.  Fraps  has  studied  the  ammonia  soluble  inorganic  soil  colloids.    He 
does  not  propose  his  method  as  a  means  by  which  the  entire  colloidal 
content  of  the  soil  may  be  measured. 

3.  The  Van  Bemmelen  Method  for  the  estimation  of  soil  colloids  con- 
sists in  the  determination  of  the  material  made  soluble  on  prolonged 
digestion  with  hydrochloric  and  sulfuric  acids.     In  the  hands  of  Blanck 
and  Dobrescu,  and  Vander  Leeden  and  Schneider,  the  Van  Bemmelen 
procedure  has  not  yielded  significant  results.     A  serious  criticism  of  the 
method  lies  in  the  fact  that  crystalloidal  as  well  as  colloidal  matter  may 
be  rendered  soluble. 

4.  The  Endosmometer  Method  has  been  used  by  Konig,  Hasenbaumer 
and  Hassler  for  the  determination  of  the  absorbed  ions  in  the  soil.    The 


THE     PHYSICAL    ACTION     OF     LIME     ON     CLAY     SOILS  5 

amount  of  salts  released  by  the  current  bears  only  a  very  indirect  rela- 
tion to  the  amount  of  colloidal  material. 

5.  The  "Pouillet  Effect"  is  another  means  by  which  the  estimation 
of  internal  surface  has  been  attempted.  This  method  is  named  after  C. 
Pouillet,  who  as  far  back  as  1823  observed  that  finely  divided  substances 
released  heat  on  wetting.  Mitscherlich  (1S98)  was  the  first  to  attempt 
the  estimation  of  the  internal  surface  of  soils  by  the  use  of  this  phe- 
nomenon. Several  other  investigators  have  since  then  attempted  similar 
studies.  The  fact  that  heat  release  in  soils  may  be  associated  with  a 
number  of  factors  renders  the  Pouillet  effect  of  doubtful  value. 

f>.  The  total  retentive  power  of  the  soil  for  water  has  long  been  used 
as  a  standard  measurement.  The  early  investigators  usually  allowed 
water  to  rise  by  capillarity  in  a  cylinder  filled  with  the  soil,  and  then 
determined  the  final  percentage  present.  Hilgard  modified  the  procedure 
by  using  a  short  column  of  standard  length,  but  the  method  still  remains 
rather  inaccurate. 

The  investigations  of  Trentler,  Wollny,  Blanck,  and  Engels  indicate 
that  calcium  oxide  increases  the  total  retentive  power  of  the  soil.  All 
these  men,  however,  used  excessive  applications.  The  probable  error  in 
the  case  of  Timer's  work  is  too  high  to  permit  the  drawing  of  conclusions. 
Frear  thinks  that  liming  has  no  effect  on  the  total  retentive  power.  The 
writer  is  calling,  attention  in  each  case  to  the  instances  in  which  limed 
soils  have  been  used,  for  there  is  no  better  criterion  as  to  the  accuracy 
of  a  physical  method,  than  its  sensitivity  to  small  amounts  of  lime. 

7.  The  Moisture  Equivalent  Method  of  Briggs  and  McLane  suggests 
itself  as  a  possible  means  for  estimating  internal  surface.    Unfortunately, 
the  probable  error  is  so  high  as  to  probably  preclude  the  measurement 
of  very  small  lime  applications.    Sharp,  of  the  California  Station,  is  using 
this  method  at  the  present  time  in  his  alkali  investigations. 

8.  The  capillary  rise   of  water  in   soil   columns  has  been   used   by 
several  investigators  as  a  method  for  estimating  soil  colloidality.     The 
usual  procedure  has  been  to  place  the  lower  end  of  a  column  of  dry  soil 
in  contact  with  water,  and  record  the  speed  and  total  height  of  ascent. 
Meve^  Krawkow,  Gross,  Blanck,  and  Engels  have  performed  capillary 
experiments  with  lime  treated  soils.     The  data,  considered  as  a  whole, 
is  inconclusive.     Undoubtedly,  internal  surface  is  a  factor  in  capillary 
rise,  but  the  additional  factors  of  surface  tension  and  degree  of  compac- 
tion are  exceedingly  difficult  to  control. 

9.  The  speed  of  percolation  of  water  through  soils  has  frequently  been 
used  as  a  measure  of  soil  structure.     Studies  have  been  conducted  by 
Yogel,  Ebermeyer,  Bfihler,  Blanck,  Thaer,  and  Engels  on  the  influence 
of  lime  on  percolation.    All  agree  that  lime  increases  the  ease  with  which 
water  passes  downward.     For  comparative  purposes  it  is  necessary  to 
obtain  a  large  volume  of  percolate,  and  this  results  in  the  removal  of 


6  THE     PHYSICAL    ACTION     OF     LIME     ON     CLAY     SOILS 

salts  from  the  sample.  An  objection  to  this  procedure  rests  in  the  fact 
that  the  colloidal  condition,  the  factor  Avhich  we  are  measuring,  depends 
on  the  salt  content.  A  decrease  in  the  amount  of  adsorbed  salts  results  in 
a  deflocculation  of  the  soils.  Both  Mayer  and  Van  Bemmelen  noted  at  an 
early  date  that  percolation  decreased  on  prolonged  leaching,  and  the  same 
thing  has  been  more  recently  noted  by  Hall,  and  by  Sharp. 

10.  The  Atterberg  Plasticity  Method  has  been  proposed  solely  as  a 
means  of  evaluating  clays.    It  has  never  been  applied  to  the  estimation 
of  internal  surface.     According  to  Kinnison,   the  Atterberg  plasticity 
figure  depends  on  too  many  factors  to  be  of  value. 

11.  The  term  "hygroscopic  moisture"  has  usually  been  taken  to  mean 
the  amount  of  water  that  a  soil  will  absorb  in  order  that  its  internal 
surface  be  covered  with  a  film  one  molecule  in  thickness.    However,  there 
is  reason  to  believe  that  the  thickness  of  the  film  is  greater  than  that 
stipulated  by  the   definition.     Furthermore,   the   slowness   in   reaching 
equilibrium,  and  the  great  effect  of  temperature  on  the  final  result,  indi- 
cate that  much  of  the  water  is  present  in  the  form  of  capillary  water 
located  in  the  interstices  of  the  soil  particles.    It  is  more  correct  to  speak 
of  the  phenomenon  as  "hygro-interstitial  moisture,"  connoting  thereby  its 
true  nature. 

The  early  workers  tested  out  the  adsorptive  power  of  soils  for  various 
vapors  and  gases.  All  these  investigations  resulted  in  the  selection  of 
water  vapor  as  best  suited  for  the  purposes  in  hand.  The  hygro-inter- 
stitial investigations  have  been  conducted  according  to  two  general  types 
of  procedure : 

1.  The  first  involves  the  constant  passage  of  water  vapor  over  or 
through  a  soil  until  equilibrium  is  reached. 

2.  The  second  requires  the  placing  of  the  sample  in  an  atmosphere 
whose  degree  of  saturation  is  controlled,  the  moisture  being  conveyed  to 
or  from  the  soil  by  diffusion. 

The  classical  investigations  of  Ammon  and  of  von  Dobeneck  belong  to 
the  first  type.  They  conducted  the  saturated  vapor  through  a  U-tube  or 
some  other  suitable  vessel  containing  the  soil,  until  equilibrium  had  been 
reached.  Both  men  were  concerned  with  the  adsorptive  power  of  the 
various  soil  constituents,  and  so  carefully  was  their  work  conducted,  that 
it  remains  today  our  most  valuable  contribution  to  the  subject. 

One  of  the  difficulties  with  the  procedure  was  the  frequency  with  which 
an  abnormal  condensation  of  water  vapor  occurred  on  the  interior  of  the 
containing  vessel.  This  led  to  the  practice  of  reducing  the  degree  of 
saturation  of  the  water  vapor.  Heiden,  for  instance,  employed  a  vapor 
a.pnroximatoly  seventy-five  per  cent  saturated,  but  he  could  not  obtain 
valuable  results.  Owing  to  the  difficulties  of  manipulation  the  subject 
was  abandoned,  and  during  the  nineties  no  work  was  done  on  any  phases 
of  the  question. 


THE     PHYSICAL    ACTION     OF     LIME     ON     CLAY     SOILS  7 

In  1903,  Kodewald  and  Mitscherlich  proposed  a  method  corresponding 
to  the  second  type  of  procedure  outlined  above.  The  soil  sample,  pre- 
viously dried  over  phosphorus  pentoxide,  was  placed  in  a  container  over 
ten  per  cent  sulfuric  acid  until  equilibrium  was  attained.  The  function 
of  the  sulfuric  acid  was  to  control  the  degree  of  humidity  and  prevent 
condensation.  This  method  has  been  used  by  a  large  number  of  investi- 
gators. Engels,  Timer,  and  Czermack  have  found  that  lime,  particularly 
calcium  oxide,  decreases  the  hygro-interstitial  moisture.  The  amounts  of 
lime  which  they  used,  however,  were  excessive. 

Comparisons  of  the  Rodenwald-Mitscherlish  method  with  the  other 
means  of  measuring  internal  surface  have  been  attempted  by  Tadokoro, 
and  Stremme  and  Aarnio.  They  find  a  good  general  agreement  between 
the  different  methods.  It  should  be  pointed  out  in  this  connection,  how- 
ever, that  a  good  general  correlation  is  to  be  expected  in  comparing  soils 
whose  percentages  of  clay  vary  widely. 

The  possibility  of  the  desiccation  over  phosphorus  pentoxide  having  an 
influence  on  the  colloidal  material  has  been  pointed  out  by  Ehrenberg 
and  Pick.  They  suggest  that  moist  soil  be  placed  in  the  desiccator  or 
humidor  and  allowed  to  remain  until  equilibrium  is  obtained. 

There  are  two  main  objections  to  the  Rodewald-Mitscherlich  method  and 
its  modifications: 

1.  Too  much  time  is  consumed  in  waiting  for  equilibrium  to  be  reached 
in  any  particular  case. 

2.  There  is  a  high  probable  error  in  the  method,  due  probably  to  the 
fact  that  diffusion  permits  only  an  approximation  of  true  equilibrium 
conditions. 

Blanck  ran  soils  according  to  the  Ehr  en  berg-Pick  modification  in  one 
instance  for  a  period  considerably  exceeding  one  hundred  days,  at  the 
end  of  which  time  equilibrium  had  not  been  reached. 

12.  The  Dye  Adsorption  Method  constitutes  one  of  the  standard  means 
for  determining  the  internal  surface  of  soils. 

Undoubtedly,  there  exists  in  the  soil  a  great  variety  of  colloidal  sub- 
stances varying  in  both  chemical  and  physical  condition.  Four  forms, 
namely,  iron,  aluminum,  humus,  and  silica,  have  been  generally  recog- 
nized. This  classification  is  of  the  crudest  sort,  and  undoubtedly  comes 
far  from  conveying  an  adequate  conception  of  the  variety  of  colloidal 
materials  present.  When  we  recall  that  the  weathering  processes  usually 
increase  the  amount  of  colloidal  matter,  we  might  expect  to  find  about 
as  many  colloids  present  in  the  soils  as  original  rock  sources.  Kogers  has 
made  a  review  of  the  mineral  kingdom,  and  finds  a  great  number  of  min- 
erals to  be  colloidal  in  nature.  Many  of  them,  we  have  reason  to  believe, 
exist  in  the  soil,  as,  for  instance,  allophane,  elemental  carbon,  opal,  hema- 
tite, and  limonite.  Soils  of  volcanic  origin  probably  contain  pyrolusite 
and  rutile. 


8  THE     PHYSICAL    ACTION     OF    LIME     ON     CLAY     SOILS 

The  use  of  dyes  iii  the  identification  of  minerals  has  been  undertaken 
by  Pelet  and  Grand,  Hundeshagen,  Dittler  and  Cornu.  Certain  dyes  are 
used  which  will  be  adsorbed  by  specific  substances,  and  thus  an  attempt 
is  made  to  identify  the  materials  present.  Unfortunately,  it  is  not  always 
possible  to  differentiate  between  the  colloidal  and  crystalloidal  matter. 
Furthermore,  it  is  possible  that  colloids  of  approximately  the  same  chem- 
ical composition  may  vary  in  their  adsorptive  powers  for  dyes.  Such 
factors  as  the  amount  of  water  of  hydration  may  quantitatively  intluence 
the  results.  Kohland  and  von  Possanner  find  that  talc  and  kaolin  vary 
widely  among  themselves  as  to  their  adsorptive  properties,  and  according 
to  Bancroft,  the  nature  of  hydrous  ferric  oxide  varies  with  the  method 
of  preparation. 

It  is  possible  that  in  the  soil  we  have  processes  which  tend  to  simplify 
the  nature  of  the  colloidal  material.  Lacroix,  in  a  study  of  the  decompo- 
sition products  of  the  aluminum  silicate  rocks,  concluded  that  the  end 
product  was  hydrous  aluminum  oxide.  Rohland  holds  the  same  view.  In 
fact,  it  seems  necessary  to  assume  an  hydrolysis  of  the  silicates  in  order  to 
explain  the  beneficial  action  following  the  application  of  calcium  silicates 
to  the  soil.  Whether  hydrolysis  takes  place  or-  not,  the  probabilities, 
nevertheless,  are  that  in  most  soils  we  have  a  vast  series  of  colloidal 
materials  present,  each  varying  somewhat  in  its  qualitative  and  quanti- 
tative adsorptive  power.  It  is,  therefore,  apparent  that  any  dyestuff  is  • 
only  very  roughly  specific  with  regard  to  its  adsorbent. 

In  view  of  the  insolved  nature  of  the  subject,  there  has  existed  in  the 
literature  the  greatest  confusion  with  regard  to  the  use  of  dyes  on  soils 
and  the  interpretation  of  the  results  obtained.  However,  the  fact  that 
certain  dyes  are  adsorbed  only  by  certain  colloids  when  prepared  in  the 
pure  state,  permits  our  obtaining  some  idea  as  to  the  nature  of  the 
adsorbing  material  in  the  field.  The  weakness  of  the  method  consists 
in  the  fact  that,  owing  to  the  variation  in  the  properties  of  the  colloidal 
matter,  our  evidence  is  circumstantial  at  best. 

Before  proceeding  further,  it  seems  necessary  to  discuss  certain  factors 
influencing  dyestuff  adsorption,  and  indicate  their  relation  to  soils  work. 

1.  Nature  of  the  dye.  The  opinion  has  existed  in  the  soils  literature 
that  all  dyes  were  equally  valuable,  as  long  as  they  were  adsorbed.  No 
idea  could  be  more  erroneous.  Lyollema  in  1905  found  that  certain  dyes 
were  specific  for  certain  materials.  The  specificity  of  dyes  has  been 
worked  out  further  by  Rohland,  and  Beaumont;  subject,  of  course,  to 
the  limitations  reviewed  in  the  preceding  pages.  We  find  that  the  azo 
dyes  are  adsorbed  practically  not  at  all.  Rohland  has  tried  to  correlate 
this  peculiarity  of  the  azo  dyes  with  certain  molecular  configurations. 
He  finds  safranine  and  indigo  (the  leuco  indigo  white?)  to  be  specific 
for  humus.  Beaumont  thinks  diamine  sky  blue  is  adsorbed  by  colloidal 
aluminum.  The  tri-phenyl  methane  dyes  are  taken  up  by  both  humus  and 


THE     PHYSICAL     ACTION     OF     LIME     ON     CLAY     SOILS 

silica.  Methylene  blue,  while  adsorbed  slightly  by  humus  and  aluminum, 
is  taken  up  in  such  enormous  amounts  by  silica,  that  it  may  be  rightly 
considered  specific  for  the  latter.  The  writer  has  found  eosin  to  be 
admirably  adapted  for  aluminum.  No  dye  has  yet  been  found  which  is 
satisfactory  for  hydrous  ferric  oxide.  Summarizing,  then,  we  have  the 
following  as  the  best  suited  for  soils  adsorption  work. 

Hydrous  ferric  oxide, — no  dye. 

Hydrous  aluminum  oxide, — eosin  and  diamine  sky  blue. 

Humus, — safranine. 

Silica, — methylene  blue. 

2.  The  concentration  of  the  dye  employed  should  be  small.     Within 
narrow  limits,  adsorption  is  a  linear  function  of  the  concentration.    The 
curve  obtained  by  plotting  the  amount  adsorbed  against  concentration 
ceases  to  be  linear,  however,  on  increasing  the  concentration  of  the  dye 
solution.    Further,  the  stability  of  the  sol  may  be  affected  if  the  dye  is 
too  concentrated. 

3.  The  dye  should  be  stable  irrespective  of  the  reaction  of  the  bath. 
All  dyes  which  in  alkaline  solution  are  changed  into  the  dye-base  or 
ICMK-O -base  are  unsuited  for  soils  which  give  an  alkaline  filtrate  on  wash- 
ing.   Inasmuch  as  the  great  majority  of  soils  render  an  aqueous  solution 
alkaline,  all  colors  exhibiting  the  above  characteristics,  as  the  tri-phenyl 
methane  dyes,  for  instance,  should  be  discarded.     Unfortunately,  this 
includes  the  greater  portion  of  the  colors  used  in  the  past,  as  crystal, 
methyl,  and  gentian  violet,  aniline  blue,  aniline  green,  aniline  red,  methyl 
green,  malachite  green,  etc.    Changing  the  reaction  of  the  solution  after 
adsorption  is  usually  not  sufficient  to  restore  the  color  to  the  dye,  since 
alkalinity  may  reduce  the  dye-base  to  the  leuco  form.    Oryng,  and  Adams 
and  Rosenstein  have  called  attention  to  the  difficulties  inherent  with  the 
triphenyl  methane  dyes.    It  is  not  surprising  that  Gedroits,  using  crystal 
and  methyl  violet,  found  no  relation  between  colloidality  and  adsorption. 

Another  potential  source  of  error  lies  in  the  fact  that  alkali  may  unite 
with  the  dye  and  form  a  lake.  This  is  what  happens  in  the  case  of  alizar- 
ine, one  of  the  dyes  recommended  by  Ljollema.  Tadokoro,  in  selecting  a 
color  for  his  work,  chose  eosin,  because  it  was  stable  in  acid  or  alkaline, 
but  he  overlooked  the  fact  that  eosin  is  specific  for  hydrous  aluminum 
oxide.  We  probably  obtain  no  eosinic  lake  formation  in  the  case  of 
adsorption  by  soils.  Too  much  care  cannot  be  taken  that  the  dye  is 
stable  under  all  conditions. 

4.  The  reaction  of  the  solution  should  not  affect  the  adsorption  equili- 
brium.    In  the  textile  industries  the  amount  of  dye  taken  up  in  any 
particular  case  is  largely  determined  by  the  degree  of  reaction  of  the 
bath.    The  subject  is  summarized  by  Bancroft  as  follows : 

The  following  holds  for  an  acid  dye: 


10  THE     PHYSICAL    ACTION     OF     LIME     ON     CLAY     SOILS 

a.  The  dye  is  taken  up  most  readily  in  an  acid  solution  but  may  be 
taken  up  in  a  neutral  or  alkaline  solution. 

b.  A  readily  adsorbed  anion  decreases  the  amount  of  dye  taken  up. 

c.  A  readily  adsorbed  cation  increases  the  amount  of  dye  taken  up. 
The  effect  of  the  reaction  on   dye  adsorption  has   been   extensively 

studied  by  Bancroft,  and  by  Pelet-Jolivet  and  his  co-workers.  If  the 
amount  of  salt  in  a  sample  of  soil  is  large,  the  final  equilibrium  may  be 
affected.  In  order  to  use  the  dye  method  as  a  measure  of  internal  sur- 
face, we  must  satisfy  ourselves  by  preliminary  experimentation  that  the 
salt  is  present  in  too  small  an  amount  to  influence  the  degree  of  adsorp- 
tion. It  is  readily  apparent  that  we  should  use  small  charges  of  soil, 
particularly  if  fertilizers  have  been  added,  for  the  amount  of  salt  per 
unit  concentration  of  dye  increases  directly  with  the  amount  of  soil 
used.  Ruprecht  and  Morse  in  their  ammonium  sulfate  studies,  found 
that  the  amount  of  dye  taken  up  by  the  soil  was  increased  after  fertilizer 
treatment.  We  have  no  means  of  knowing  from  their  work,  however, 
whether  the  increase  was  due  to  the  influence  of  the  ammonium  sulfate 
on  internal  surface,  or  whether  it  was  the  result  of  the  changed  reaction 
of  the  bath.  The  effect  of  the  added  material  on  the  adsorption  equili- 
brium has  been  in  the  past  entirely  overlooked  in  soils  work. 

5.  The  protective  action  of  organic  matter  on  colloidal  material  has 
been  recognized  by  a  number  of  investigators.  In  running  experiments 
on  mineral  colloids  it  is  desirable  to  use  soils  as  free  from  organic  matter 
as  possible. 

13.  Selective  adsorption  has  been  used  by  many  investigators  as  a 
means  of  estimating    internal    surface.      Heiden,   Parker,   and  Konig, 
Hasenbaumer,  and  Hassler  are  only  a  few  of  those  who  have  taken  the 
adsorptive  power  of  the  soil  for  potassium  as  a  measure  of  the  internal 
surface  involved.    The  results  lose  their  significance,  however,  when  we 
recall  that  the  soil  contains  a  number  of  different  kinds  of  colloidal 
material,  each  varying  in  its  specificity  with  regard  to  adsorption.    Thus, 
Thaer  finds  that  the  potassium  ion  is  not  adsorbed  by  colloidal  humus, 
and  Lokolovskii  observes  the  same  thing  for  the  ammonium  radical. 
Daikuhara  believes  that  the  adsorption  of  the  potassium  ion  is  character- 
istic of  the  colloidal  iron  and  aluminum.    The  possibility  of  interchange 
of  bases  tends  to  further  confuse  the  phenomenon.    It  is,  therefore,  not 
surprising  that  some  workers,  as  Tadokoro,  have  failed  to  establish  an 
agreement  in  the  results  from  selective  adsorption  and  some  of  our  other 
more  valuable  methods. 

14.  The  Histological  Method  for  the  determination  of  colloids  in  clays 
was  proposed  by  Endell.    The  dry  clay  is  boiled  in  Canada  balsam,  and 
after  cooling  and  hardening  it  is  cut  into  small  sections  and  colored  with 
fuchsin.    This  method  has  been  discussed  by  Cornu.    Owing  to  the  sim- 


THE     PHYSICAL    ACTION     OF     LIME     ON     CLAY     SOILS  11 

plicity  of  certain  other  procedures,  the  histological  method  has  never 
come  into  general  use. 

15.  Expansion  methods  are  nearly  as  old  as  soil  physics  itself.     In 
1838,  Schiibler  began  work  on  the  subject,  and  his  investigations  have 
been  continued  by  Haberlandt,  von  Schwarz,  Puchner,  and  Wollny.    The 
lime  studies  of  Thaer  and  Engels  resulted  in  the  conclusion  that  there 
was  a  slight  increase  in  volume  on  liming.     In  all  the  above  cases  the 
soils  were  allowed  to  come  to  dryness  before  making  final  measurements. 
Tempany   (1917)   finds  that  in  drying  down,  internal  friction  between 
the  soil  particles  becomes  very  great.     This  raises  the  question  whether 
measurements   after   drying   are   particularly   significant.     Brown   and 
Montgomery,  in  a  study  of  the  dehydration  of  clays,  finds-  that  shrinkage 
is  no  criterion  of  plasticity.    Furthermore,  it  appears  just  as  objection- 
able to  make  measurements  from  a  dry  to  a  moist  condition,  as  vice  versa. 
R.  O.  E.  Davis  cites  data  from  Wollny  in  which  the  latter  found  that  a 
dry  soil  moistened  with  water  expanded  six  times  as  much  as  the  same 
soil  moistened  with  calcium  hydrate  solution! 

Wolff,  and  more  recently  Tadokoro,  have  studied  the  swelling  exhibited 
by  soils  after  being  immersed  in  various  reagents.  This  work  is  open 
not  only  to  the  objections  already  mentioned,  but  is  also  subject  to  the 
further  criticism  that  swelling  may  be  specific  for  the  reagent  employed. 
If  expansion  readings  are  made  at  a  constant  moisture  content,  we 
largely  eliminate  imbibitional  factors,  and  may  more  correctly  attribute 
differences  to  changes  in  soil  structure. 

16.  The  cohesion  method  for  the  investigation  of  soil  properties  was 
first  used  by  Rchtibler,  who  added  a  gradually  increasing  weight  to  a 
scale  pan  suspended  from  the  middle  of  the  dry  brickette  to  be  tested. 
This  procedure  has  been  used  by  Fippin  in  his  investigation  of  the  effect 
of  lime  on  granulation.     The   Schiibler  method   has  been  modified   by 
Puchner,  who  suspends  the  scale  pan  above  the  knife  edge  entering  the 
soil.    The  Atterberg  procedure  is  essentially  the  same  as  that  of  Puchner, 
except  that  the  scale  pan  is  supported  by  a  superstructure.    The  penetra- 
tion method  has  been  used  by  Cameron  and  Gallagher,  and  by  R.  O.  E. 
Davis  for  measuring  coherence.     The  greater  portion  of  their  work  is 
unconvincing  because  they  failed  to  calculate  the^  probable  error  of  their 
determinations.    Thaer  and  Engels  have  made  penetration  measurements 
in  their  work,  but  unfortunately  the  amounts  of  lime  used  were  excessive. 

It  would  seem  that  penetration  determinations  should  be  made  at  a 
constant  moisture  content  for  essentially  the  same  reasons  as  in  the  case 
of  shrinkage.  On  bringing  to  air  dryness,  certain  cementing  materials 
undoubtedly  con>e  into  play  which  are  not  operative  under  ordinary  con- 
ditions. 

17.  The  Dynamometer  Method  consists  in  measuring1  the  resistance 
offered  to  the  passage  of  a  plow  through  the  soil.     A  spring  is  connected 


12  THE     PHYSICAL    ACTION     OF     LIME     ON     CLAY     SOILS 

with  a  revolving  drum  in  such  a  manner  as  to  record  the  traction  at  any 
particular  moment.  We  would  expect  that  the  summations  of  the  values 
ob'tained  from  various  lime  plats,  for  instance,  would  indicate  the  effect 
of  the  lime  on  the  physical  condition  of  the  soil.  Work  along  this  line 
has  been  undertaken  by  Alausberg  and  by  Noll.  Unfortunately  the  prob- 
able error  involved  is  so  high  that  experiments  must  be  carried  through  a 
long  series  of  years  before  significant  results  are  obtainable. 

18.  The  Oxidative  Power  of  the  soil  has  never  been  used  as  a  method 
for  the  estimation  of  internal  surface.  There  seems  no  reason  to  doubt, 
however,  that  oxidation  is  in  large  part  a  surface  phenomenon.  The 
great  ability  of  colloidal  humus  and  hydrous  ferric  oxide  to  cause  oxida- 
tion, as  indicated  by  the  work,  of  Schreiner  and  his  co-workers,  would 
suggest  that  oxidation  may  be  a  specific  and  not  a  general  phenomenon. 

Aloin  is  not  suited  for  measurements  of  internal  surface,  owing  to  the 
fact  that  it  is  catalyzed  by  alkalies.  An  aloin  solution  will  "keep"  for 
only  a  few  hours  because  of  the  presence  of  alkali  dissolved  from  the  con- 
tainer. An  aloin  solution  will  keep  indefinitely  if  a  small  amount  of 
acid  is  added  when  the  solution  is  first  made.  The  question  arises  in 
this  connection  whether  Schreinor  and  Sullivan's  study  of  the  oxidizing 
power  of  soil  extracts  is  particularly  significant. 

Phenolphthalin  is  more  satisfactory  for  estimating  internal  surface.  Tt 
is  convenient  to  read,  and,  unlike  aloin,  is  very  stab'le  towards  the  atmos- 
phere. One  precaution  to  be  observed,  is  to  avoid  the  use  of  a  strong 
alkali  in  bringing  out  the  full  color  of  the  phenolphthalein  before  reading. 
In  a  strongly  alkaline  solution  the  phenolphthalein  is  converted  into  the 
colorless  leuco-basc.  Ammonia  is  a  very  satisfactory  alkali  to  use  in 
this  connection. 

It  is  frequently  desirable  to  clarify  the  solution  with  a  precipitant, 
just  prior  to  rendering  the  solution  alkaline.  If  a  soil  has  been  rendered 
strongly  basic  by  a  salt  treatment,  the  humus  brought  into  suspension 
may  modify  the  pink  color  to  such  a  degree  as  to  make  a  previous  precipi- 
tation imperative. 

DISCUSSION 

In  the  preceding  exposition  we  noted  that  the  analogy  between  the 
suspension  method  and  conditions  as  they  actually  exist  in  the  soil,  was 
not  very  close.  There  is  no  reason  to  doubt,  however,  that  the  funda- 
mental phenomena  involved  are  essentially  the  same,  the  differences 
being  simply  a  matter  of  degree.  Cameron  takes  the  point  of  view  that 
there  is  no  basis  for  attributing  surface  action  to  colloids,  ami  Oedroits 
holds  a  similar  opinion,  on  account  of  the  small  colloidal  content  of  any 
soil.  On  taking  into  consideration  the  large  internal  surface  involved 
on  even  a  slight  subdivision  of  any  material,  however,  it  is  found  nnneces- 


THE    PHYSICAL    ACTION    OF    LIME     ON    CLAY    SOILS  13 

sary  to  stipulate  any  other  action  to  account  for  the  surface  phenomena 
which  take  place. 

A  consideration  of  the  literature  on  the  effect  of  lime  salts  on  floccula- 
tion  reveals  an  unusual  amount  of  confusion.  The  relation  of  valence  to 
flocculating  power  has  long  been  appreciated,  but  unfortunately  invetiga- 
tors  are  just  coming  to  realize  that  the  question  of  active  masses  is  of 
equal  importance.  For  instance,  sodium  salts  of  weak  acids  are  floccu- 
lents  or  defiocculents  according  to  the  relative  concentrations  of  pre- 
cipitant and  material  being  precipitated.  This  question  has  been  dis- 
cussed in  detail  by  Given,  Wolkoff,  and  Wiegner. 

Rohland  believes  that  on  liming,  the  precipitating  power  is  due  to 
hydroxyl  ions,  and  with  calcium  hydrate,  the  action  is  direct.  With  cases 
in  which  gypsum  is  applied,  Rohland  would  assign  the  beneficial  result  to 
the  precipitating  power  of  the  hydroxyl  ions  formed  on  the  decomposi- 
tion of  the  salt.  Here  again,  the  various  colloidal  materials  present  in 
the  soil  tend  to  further  confuse  the  phenomenon.  Pappada  finds  that 
the  hydroxyl  ion  is  the  most  powerful  in  the  precipitation  of  hydrous 
ferric  oxide.  Rohland's  view  would  hold  in  so  far  as  the  positive  colloids 
are  concerned,  but  it  would  not  hold  for  the  negative.  A  soil  suspension 
is  usually  negative,  but  there  is  no  ground  to  believe  that  the  colloidal 
material  in  the  soil  is  entirely  precipitated  by  cations  or  other  bodies 
positively  charged. 

Ehrenberg  holds  that  the  cation  is  the  important  flocculating  agent. 
He  ascribes  a  strong  action  to  the  calcium  ion,  and  virtually  none  to  the 
hyfroxyl.  Therefore1  calcium  hydrate  is  the  strongest  flocculent  of  the 
lime  salts.  On  increasing  the  strength  of  the  acid  in  the  salt,  the  pre- 
cipitating action  becomes  less  and  less,  until  in  the  case  of  gypsum,  we 
have  practically  complete  antagonism.  Ehrenberg's  theory  is  better  than 
Rohland's  just  in  so  far  as  it  better  describes  the  actual  state  of  affairs. 
As  a  matter  of  fact,  both  views  are  extreme.  A  solution  of  the  question 
lies  in  the  recognition  of  the  complex  nature  of  the  colloidal  material, 
and  the  fact  that  flocculation  is  a  matter  of  relative  charges,  masses, 
and  valencies. 

In  past  studies  on  the  physical  effect  of  lime  on  the  soil,  the  tendency 
has  been  to  make  applications  on  a  percentage  basis.  For  example,  a 
favorite  custom  has  been  to  use  one  per  cent  of  lime,  and  there  is  one 
instance  in  the  literature  in  which  one  part  of  lime  was  added  to  four 
parts  of  soil.  In  view  of  the  relation  of  masses  to  precipitation,  and 
furthermore,  the  wide  departure  from  field  practice  involved,  the  question 
naturally  arises  whether  the  results  from  such  experiments  are  particu- 
larly  significant.  The  work  of  Blanck,  Thaer,  and  Engels,  the  lime 
studies  most  frequently  quoted,  are  all  open  to  the  objection  that  the 
applications  used  were  excessive.  Unfortunately  the  methods  available 
for  physical  studies  have  not  been  sufficiently  accurate  to  be  used  in 


14 


THE     PHYSICAL     ACTION     OF     LIME     ON     CLAY     SOILS 


work  with  comparatively  small  salt  applications.  In  the  present  investi- 
gation, an  attempt  was  made  to  obtain  data  from  applications  equal  to 
and  smaller  than  the  lime  requirement  of  the  soil,  in  order  to  more  nearly 
approximate  field  conditions. 

EXPEKIMENTAL  STUDIES 

All  the  soils  used  were  of  the  Dunkirk  silt  loam  series,  and  were 
obtained  from  two  stations  on  the  Cornell  University  farm.  In  addition, 
work  was  undertaken  with  samples  from  the  lime  plots  on  Caldwell  Field. 
All  the  soils  analyzed  approximately  the  same  mechanically. 

TABLE  I.     MECHANICAL  ANALYSIS  OF  DUNKIRK  SILT  LOAM  SOILS 


Soil  Tech.  Plats 
and  Station  I 

Station  11 

Total  sands 

13  '.)'  , 

OS', 

Silt.. 

<>7  4 

71   9 

Clav  

18  6 

18  3 

Unpublished  results  of  bulk  analyses  give: 


TABLE  II.     BULK  ANALYSES  OF  DUNKIRK  SILT  LOAM  SOIL 
(From  9  samples  of  Tonipkins  County  soil) 


„ 

Surface  '  j 

Subsoil 

C.   (organic  carbon). 

1    C>70 

0  440 

CO2... 

trace 

0  260 

K2O  

1  740 

2  110 

CaO  

0  430 

0  830 

MgO.. 

0  450 

0  690 

Na2O... 

1  090 

1  280 

N... 

0  186 

0  082 

P2O5  

0  123 

0  126 

In  sampling  the  soil  in  the  field,  care  was  taken  to  get  well  down 
below  the  sod  line  in  order  that  organic  matter  be  excluded  as  far  as 
possible.  The  material  was  brought  in  to  the  laboratory,  put  through  a 
coarse  sieve,  and  well  mixed.  The  soil  had  an  acidity  of  3000  pounds  of 
calcium  oxide  per  acre,  as  determined  by  the  Veitsch  method.  All  the 
limes  used  were  200  mesh,  and  pots  were  set  up  with  calcium  hydrate, 
limestone,  precipitated  calcium  carbonate,  gypsum,  and  precipitated  cal- 
cium sulfate.  In  addition,  studies  were  conducted  with  precipitated 
basic  magnesium  carbonate,  and  sodium  carbonate.  The  limes  were  added 
in  molecularly  equivalent  amounts,  and  proper  corrections  were  made 


THE     PHYSICAL     ACTION     OF     LIME     ON     CLAY     SOILS  15 

for  magnesium  in  the  limestone  (it  was  nearly  pure),  and  for  water  of 
hydration.  Applications  were  made  in  the  equivalents  of  one-half, 
one  and  one-half,  four  and  one-half,  and  ten  tons  of  calcium  oxide  per 
acre,  taking  two  and  one-half  million  pounds  as  the  weight  of  an  acre — 
eight  inches  of  soil.  The  one  and  one-half  ton  treatment  exactly  corre- 
sponded with  the  lime  requirement  of  the  soil.  Into  each  pot  was 
weighed  the  equivalent  of  253  grams  of  oven  soil.  The  container  was 
given  a  prolonged  tamping,  two  thicknesses  of  cotton  gauze  added,  and 
finally  a  mulch  of  washed  quartz  sand  placed  on  top  to  a  thickness  of  one 
centimeter.  Aerated  distilled  water  was  added  to  bring  the  pots  up  to 
24  or  28  per  cent  water  content,  at  which  they  were  maintained  for  the 
remainder  of  the  experiment.  (Note:  all  references  to  water  content 
in  this  treatise  are  on  an  oven  dry  basis.)  A  portion  of  the  series  were 
set  up  in  triplicate;  the  rest  in  quadruplicate.  The  duration  of  the 
experiments  was  45, 100,  and  225  days.  On  the  expiration  of  the  required 
time,  the  mulches  were  removed,  the  soil  sieved  (20  mesh),  dried  down 
to  7-10  per  cent,  and  bottled.  The  soils  were  never  allowed  to  reach  air 
dryness. 

In  the  exposition  on  procedures  for  estimating  internal  surface, 
eighteen  methods  were  examined  as  to  their  respective  merits.  We  found 
that  the  great  majority  are  for  one  reason  or  the  other  inaccurate.  Six 
of  them  were  used  in  the  present  investigation,  namely, — 

1 .  Penetration. 

2.  Expansion. 

3.  Total  retentive  power. 

4.  Dye  adsorption. 

5.  Hygro-interstitial  water. 

6.  Oxidative  power. 

EFFECT  OF  SALTS  ON  PENETRATION 

The  apparatus  used  for  the  measurement  of  penetrability  was  the 
Atterberg  apparatus  as  improved  by  Prof.  H.  O.  Buckman  of  Cornell 
University.  The  feature  worthy  of  particular  attention  is  the  device  for 
controlling  the  distance  that  the  pin  enters  the  soil.  With  the  pin  point 
flush  with  the  surface  of  the  soil,  the  mercury  well  may  be  set  so  that  the 
metal  point  on  top  just  makes  contact  with  a  similar  point  on  the  piston. 
The  distance  from  this  position  to  the  surface  of  the  mercury  is  constant, 
and  represents  the  distance  which  the  pin  penetrates.  Water  is  used  to 
give  the  gradually  increasing  force  to  the  head  of  the  piston.  On  receiv- 
ing the  signal  from  the  sounder,  the  water  is  stopped,  and  the  weight  in 
the  container  is  determined.  This  value  represents  the  penetrability  of 
the  particular  soil  concerned. 

A  series  which  had  run  for  100  days  was  used  for  the  penetration 
determinations,  and  in  order  to  avoid  the  results  incidental  to  air  drying, 


16 


THE    PHYSICAL    ACTION    OF    LIME     ON    CLAY    SOILS 


readings  were  made  when  the  moisture  percentage  of  the  soil  was'  between 
14-15  per  cent.  Five  readings  were  attempted  in  each  pot,  and  since  the 
series  was  in  triplicate,  fifteen  readings  per  treatment  were  obtained. 

TABLE  III.     PENETRATION  IN  GRAMS  OF  SOILS  LIMED  FOR  100  DAYS 
(Each   figure  is  the  average  of  15  determinations) 


v 

Chocks 
(no  treat.) 

Ca(3H)2 

Li  mo- 
st one 

pCaCOs 

Gypsum 

Na2CC3 

Vi  T 

1148 

1716 

2157 

4137 

P.  E. 

115 

39 

1*9 

339 

\y2  T. 

709 

1046 

2374 

1912 

4499 

P.  E. 

196 

37 

152 

182 

451 

P.  E.  ] 
10  T. 

787 
83 

392 
29 
306 

904 
27 
694 

2294 
117 

1832 
132 

1737 

4678 
534 
3722 

P.  E. 

15 

34 

73 

387 

While  the  probable  error  in  some  cases  is  rather  high,  nevertheless, 
we  may  draw  the  general  conclusion  that  calcium  hydrate  decreases  sur- 
face penetrability  more  than  any  of  the  other  salts  tried.  One  thing 
worthy  of  note  is  that  calcium  carbonate  seemed  to  increase  the  value 
when  used  in  small  amounts.  Unfortunately  the  question  of  crust  forma- 
tion enters  in,  and  tends  to  confuse  the  results.  There  is  virtually  no 
hardening  on  the  surface  of  the  untreated  soil,  while  those  to  which  has 
been  added  a  half  a  ton  of  lime  per  acre  may  form  quite  a  tough  crust, 
as  in  the  case  of  the  gypsum  treatments.  What  our  results  indicate, 
then,  is  that  calcium  hydrate  causes  the  formation  of  a  less  impervious 
crust  than  any  other  lime.  If  the  penetration  method  is  to  be  used  as  a 
measure  of  the  internal  and  not  the  surface  condition,  the  crust  must  be 
removed. 

Penetration  studies  on  the  interior  portion  of  the  soil  were  attempted. 
Brass  pins  of  various  shapes  and  sizes  were  advanced  into  the  soil  with 
the  ratchet  of  the  micrometer  used  in  connection  with  the  expansion 
studies.  The  distance  that  the  ratchet  forced  the  pin  into  the  soil  was 
read  directly  on  the  micrometer  scale.  (The  crust  had  been  removed.) 
The  results  failed  to  show  significant  differences  between  the  different 
salt  treatments.  We  may  therefore  conclude  that  the  influence  of  salt 
treatment  is  primarily  on  crust  formation,  in  so  far  as  the  penetration 
method  is  a  proper  criterion.  It  cannot  be  used  for  very  sensitive  meas- 
urements, because  it  is  subject  to  a  number  of  uncontrolled  factors. 

EXPANSION  STUDIES 

It  was  evident  from  the  preliminary  discussion  that  we  would  expect 
flocculation  and  expansion  to  go  hand  in  hand.  Furthermore,  it  seemed 
that  expansion  studies  should  be  conducted  at  a  constant  moisture  con- 


THE     PHYSICAL    ACTION     OF     LIME     ON     CLAY     SOILS 


17 


tent.  In  order  to  observe  expansions  under  these  conditions,  a  series 
which  was  running  for  100  days  was  selected  for  special  experimenta- 
tion. Measurements  were  made  according  to  a  method  suggested  by 
Professor  J.  A.  Bizzell  of  Cornell  University.  A  ratchet  micrometer  was 
fastened  to  a  standard  so  that  the  spindle  head  could  play  on  a  brass 
pin  which  projected  three-fourths  of  an  inch  above  the  surface  of  the 
soil.  The  pin  passed  perpendicularly  through  the  middle  of  a  small  brass 
plate,  the  latter  resting  on  the  soil  surface.  The  pin  was  further  steadied 
by  a  projection  passing  down  into  the  soil.  A  reading  was  made  by 
lowering  the  micrometer  spindle  gently  in  to  the  pin,  until  there  was 
a  constant  "pull"  on  the  slip  of  thin  paper  inserted  between  pin  and 
spindle.  This  method  is  accurate  to  the  hundredth  of  a  millimeter. 

In  setting  up  the  experiment,  pins  were  placed  on  the  one-half,  one 
and  one-half,  and  ten  ton  treatments  only.  The  initial  reading  was 
made  three  hours  after  the  pots  had  been  brought  up  to  weight.  During 
the  course  of  the  experiment  readings  were  taken  from  time  to  time; 
in  each  case,  however,  24  hours  after  watering,  inasmuch  as  approxi- 
mately 24  hours  were  required  to  evaporate  the  water  from  the  quartz 
mulch. 

EFFECT  OF  TIME  AND  SALTS  ON  SOIL  EXPANSIONS 

(Each  figure  in  the  following  data  is  the  average  of  quadruplicate  determinations. 
The  values  all  have  a  negative  sign,  i.  e.,  there  was  contraction  in  every  case. 
Readings  are  in  mm.) 


Treatment 

14  Days 

1 
25  Days 

35  Days 

45  Days 

90  Days 

No.  treatment.  . 

1.76 

2.14 

2.44 

3.31 

3  33 

P.  E  

.18 

27 

25 

26 

34 

Ca(OH)2 
Y2  T 

1.49 

1  85 

2  19 

2.76 

3  31 

\y2  T  . 

.20 

88 

.09 
1  31 

.07 
1  59 

.09 
2  17 

.08 
2  60 

10  T  

.12 
.34 

.17 

.58 

.21 
.79 

.14 
1.22 

.18 
1.39 

Limestone 
Y2  T  

.03 
1.20 

.02 
1.56 

.03 
1.76 

.02 
2.31 

.03 

2.68 

\Y*  T 

.18 
1  61 

.18 
1  95 

.15 
2  35 

.18 
2  86 

.32 
3  21 

10  T  

.13 

.55 

.13 
.70 

.14 
1  03 

.15 

1.49 

.15 
1.72 

p.  CaCOs 

y2T  .- 

.08 
.98 

.10 
1  50 

.09 
1  84 

.10 
2.44 

.13 
2.96 

iy2  T..  

.15 

86 

.23 
1  35 

.27 

1  76 

.30 
2.33 

.49 
3.03 

.07 

10  T  

90 

1  46 

1  74 

2.31 

3.03 

p.  CaSO4 

y2T  

.04 
.57 

.08 
1.03 

.04 
1.21 

.04 
1.67 

.07 
1.97 

.12 

.14 

.12 

.12 

.18 

18  THE     PHYSICAL    ACTION     OF     LIME     ON     CLAY     SOILS 

EFFECT  OF  TIME  AND  SALTS  ON  SOIL  EXPANSIONS — Continued 


Treatment 

14  Days 

25  Days 

35  Days 

45  Days 

90  Days 

\y2  T 

71 

1  33 

1  55 

1.89 

2.20 

10  T 

.11 

77 

.1.5 
1  06 

.15 

1  22 

.06 
1.73 

.09 
1.87 

p.  MgCO3  (basic) 

y2  T.  . 

.04 
92 

.04 
1  49 

.04 

1  86 

.06 

.08 
2.95 

11AT      . 

.08 
1  28 

.15 
2  11 

.16 
2  46 

.18 
3.47 

19 

17 

.18 

.25 

10  T.  .    . 

1  73 

2  05 

2  26 

3.71 

18 

29 

25 

.44 

Na2CO3 
M  T  

.89 

1.19 

\y2  T  

• 

.13 

.89 

.25 
2.02 

10  T  

.44 
3.24 

.51 

3.83 

.60 

.67 

We  see  from  the  above  data  that  the  contraction  with  the  calcium 
hydrate  treatments  is  decidely  less  than  with  the  limestone.  There  is  not 
much  difference  between  the  limestone  and  precipitated  carbonate  data 
when  small  applications  were  employed.  The  limestone  seemed  to  be 
superior  to  the  precipitated  carbonate,  however,  when  large  applications 
were  used.  There  was  less  contraction  with  the  soils  to  which  precipitated 
calcium  sulfate  had  been  added  than  with  any  of  the  others.  In  this 
connection  it  should  be  noted  that  a  smaller  contraction  than  the  check 
does  not  necessarily  imply  a  greater  expansion.  Anything  causing  an 
abnormal  solidification  of  the  soil  mass  may  be  wrongly  interpreted  as 
an  expansion.  In  the  case  of  the  sodium  carbonate  pots  we  probably 
have  this  action.  The  precipitated  magnesium  carbonate  seems  to  exert 
no  particularly  striking  effect. 


EFFECT  OF  LIMING  ON  THE  TOTAL  RETENTIVE  POWER 

The  determinations  were  carried  out  in  the  following  manner:  A  soil 
of  known  moisture  content  was  poured  into  a  weighed  Hilgard  cup,  in  the 
bottom  of  which  was  a  filter  paper.  After  tamping  a  definite  number  of 
times  the  top  portion  was  struck  off  with  a  straight-edge,  and  then  the 
cup  and  soil  weighed.  Knowing  the  moisture  content  of  the  soil,  the 
dry  weight  equivalent  in  the  cup  could  be  easily  determined.  The  cup 
was  then  set  into  water  in  a  thermostat  so  that  there  would  just  be 
capillary  contact.  After  the  soils  had  become  thoroughly  saturated  (a 
matter  of  several  hours),  the  cups  were  set  aside  to  drain,  after  which 
they  were  wiped  dry,  and  weighed.  A  calculation  of  the  amount  of 


THE     PHYSICAL    ACTION     OF     LIME     ON     CLAY     SOILS 


19 


capillary  water  taken  up  by  the  soil,  based  on  the  oven  dry  weight,  was 
then  made. 

Below  are  tabulated  the  results  with  treatments  which  had  run  for  100 
and  225  days,  respectively.  Each  figure  in  the  following  tables  is  an 
average  of  six  or  eight  determinations. 

RETENTIVE  POWER  OF  SOILS  LIMED   100   DAYS:     SERIES  I 


Treatment 

Ca(OH)2 

Lime- 
stone 

p.CaCO.3 

Gypsum 

Na2C03 

Checks 

J^T.. 

49.1 

50.1 

51.6 

52.8 

52.2 

P.  E  

1.6 

1.1 

.9 

.6 

1.6 

l^T  
P.  E... 

50.5 
1.2 

51.5 
1.1 

52.0 
.9 

53.4 
1.2 

47.6 
.6 

4^T  
P.  E... 
10  T  
P.  E  

49.0 
1.7 
49.2 
1.6 

51.0 
1.2 
49.3 
2.0 

51.6 
.9 
50.9 
1.3 

56.2 
1.1 
54.3 

.8 

44.5 
.5 

48.2 
.8 

50.3 
1.1 

RETENTIVE  POWER  OF  SOILS  LIMED  100  DAYS:     SERIES  II 


Treatment 

^T. 

1HT. 

10  T. 

Checks 

Ca(OH)2  ...... 

57.1 

55.3 

56  5 

1.0 

1.0 

5 

p.  CaCO3. 

59.3 

56  9 

59  3 

P.  E. 

8 

9 

3 

Limestone 

56  2 

57  9 

55  3 

56  8 

P.  E. 

2  34 

1  6 

1  9 

3 

p.  CaSO4 

54  7 

57  6 

54  4 

P.  E  .  .  . 

3.5 

1.4 

1.1 

Na2GO3.- 

49.6 

47.1 

48.0 

P  E 

6 

7 

4 

M.  MgCO3... 

54.6 

54.4 

58.7 

P.  E  

.9 

1.8 

.8 

RETENTIVE  POWER  OF  SOILS  LIMED  225  DAYS:     SERIES  I 


Treatment 

Ca(OH)2 

Lime- 
stone 

p.  CaCO3 

Gypsum 

Na2CO3 

Checks 

1A  T.  . 

51.3 

48  3 

51  9 

54  1 

51  0 

P.  E 

6 

1  0 

4 

1  3 

1.5 

11AT  
P.  E. 

52.1 
.5 

50.2 
1  6 

55.1 
6 

52.8 
5 

46.7 
1  5 

53.1 
4 

4^2  T. 

50  8 

52  0 

56  2 

52  2 

47  2 

P.  E. 

5 

1  2 

3 

2  3 

1  2 

10  T  
P.  E. 

51.0 
8 

49.4 
2 

54.0 
1 

50.6 
1  2 

50.2 
1 



20  THE     PHYSICAL     ACTION     OF     LIME     ON     CLAY     SOILS 

It  may  be  readily  observed  that  none  of  the  salts  affected  the  total 
retentive  power  in  the  case  of  the  salts  run  100  days,  with  the  exception 
of  the  sodium  carbonate.  With  the  225  day  treatment,  however,  we  find 
that  both  calcium  hydrate  and  limestone  have  caused  a  slight  decrease 
in  water  holding  capacity.  The  precipitated  carbonate  may  act  in  just 
the  opposite  direction.  The  gypsum  is  without  effect. 

DYE  ADSORPTION  STUDIES 

In  the  preliminary  discussion,  attention  was  called  to  the  fact  that 
certain  factors  affecting  dye  adsorption  have  been  entirely  overlooked 
in  studies  with,  soils.  Perhaps  the  most  important  of  these  factors  are, 
the  stability  of  the  dye,  and  the  effect  of  salts  on  the  adsorption  equilib- 
rium. There  are,  however,  several  other  questions  that  arise  in  this 
connection : 

What  is  the  influence  of  the  time  of  shaking  on  the  adsorption  equilib- 
rium, and 

Does  the  mechanical  agitation  incidental  to  shaking  tend  to  destroy  the 
flocculated  condition,  and  hence  affect  the  degree  of  adsorption? 

In  order  to  study  the  effect  of  time  of  shaking,  adsorptions  were  run 
and  terminated  at  regular  intervals.  Using  two  grams  of  Dunkirk  silt 
loam  in  methylene  blue,  it  was  found  that  complete  equilibrium  was 
reached  in  from  one  to  two  hours. 

The  effect  of  mechanical  agitation  on  adsorption  was  studied  by 
adding  two  grams  of  soil  to  solutions  in  shaker  bottles,  the  latter  con- 
taining the  amount  of  salt  that  would  be  carried  over  in  a  two  gram 
charge  of  soil  treated  at  the  rate  of  10  tons  per  acre.  After  shaking  two 
hours,  a  few  cc.  of  a  concentrated  methylene  blue  solution  was  added, 
and  the  shaking  continued  for  five  minutes  longer.  The  results  showed 
that  final  equilibrium  had  not  been  affected  by  the  salts  present,  with 
the  exception  of  the  sodium  and  magnesium  carbonate  treatments,  and 
in  these  cases  we  do  not  have  to  postulate  any  change  in  stability  of  the 
colloidal  material,  inasmuch  as  the  solutions  were  very  alkaline,  and 
hence  could  affect  the  adsorption  equilibrium.  The  subject  was  studied 
still  further  by  running  adsorptions  in  methylene  blue,  and  determining 
whether  the  final  result  was  the  same  irrespective  of  the  salt  present. 
Here  again,  the  sodium  and  magnesium  carbonates  were  found  to  increase 
adsorption  somewhat. 

Adsorption  experiments  with  methylene  blue  were  run  as  follows: 
The  equivalent  of  2  grams  of  oven  soil  was  weighed  into  the  shaker 
bottle  containing  100  cc.  of  the  dye  (.25  gram  per  litre).  After  shaking 
two  hours,  the  clear  supernatant  solution  was  read  against  a  standard. 
The  results  with  soils  which  had  been  limed  for  100  and  225  days  are 
as  follows: 


THE     PHYSICAL    ACTION     OF     LIME     ON     CLAY     SOILS 


21 


ADSORPTION  OF  METHYLENE  BLUE  BY  SOILS  TREATED  FOR  100  DAYS 
(Readings  in  divisions  equivalent  to  100  of  standard) 


Treatment 

Ca(OH)2 

Lime- 
stone 

p.  CaCO3 

Gypsum 

Checks 

1A  T... 

272 

217 

144 

180 

l^T  
±1A  T 

208 
153 

190 
163 

159 
112 

153 
118 

235 

10  T 

70 

143 

100 

110 

ADSORPTION  OF  METHYLENE  BLUE  BY  SOILS  TREATED  FOR  225  DAYS 


Treatment 

Ca(OH)2 

Lime- 
stone 

p.  CaCO3 

Gypsum 

14  T... 

183 

210 

168 

114 

1  1/2  T   .  .  .      . 

162 

151 

163 

95 

4^2  T   . 

117 

138 

140 

106 

10  T 

57 

139 

133 

82 

Each  figure  in  the  preceding  tables  is  the  average  of  triplicate  deter- 
minations. While  calcium  hydrate  decreases  adsorption  the  most  when 
10  ton  treatments  are  used,  precipitated  carbonate  and  gypsum  are  more 
efficient  with  slight  applications. 

Studies  were  conducted  with  safranine  in  order  to  observe  the  effect 
of  salts  in  the  adsorptive  power  of  the  organic  matter.  Preliminary 
experiments  indicated  that  adsorptions  could  not  be  conducted  with 
safranine  in  the  presence  of  sodium  and  magnesium  carbonates.  The 
results  are  as  follows : 

ADSORPTION  OF  SAFRANINE  BY  SOILS  TREATED  FOR  45  DAYS 


Treatment 

Check 

Ca(OH)2 

Lime- 
stone 

p.  CaCO3 

Gypsum 

l^T.. 

52 

52 

62 

60 

10  T  

51 

44 

45 

42 

62 

ADSORPTION  OF  SAFRANINE  BY  SOILS  TREATED  FOR  225  DAYS 


Treatment 

Check 

Ca(OH)2 

Lime- 
stone 

p.  CaCO3 

Gypsum 

11A  T.. 

47 

60 

61 

34 

10  T  

51 

42 

61 

61 

34 

22 


THE     PHYSICAL     ACTION     OF     LIME     ON     CLAY     SOILS 


With  the  soils  treated  for  45  days,  liming  seemed  to  decrease  the 
adsorptive  power  when  applied  in  excessive  amounts.  The  same  applies 
to  calcium  hydrate  and  gypsum  for  the  225  day  treatments.  On  the 
other  hand,  limestone  and  precipitated  carbonate  increased  the  adsorp- 
tive power  slightly.  It  may  be  that  the  analogy  of  internal  surface  does 
not  apply  to  organic  matter,  and  that  the  influence  of  salts  on  the 
adsorptive  power  is  primarily  chemical  rather  than  physical. 

Adsorption  experiments  were  conducted  with  diamine  sky  blue  and 
with  diamine  violet,  both  of  which  are  specific  for  hydrous  aluminum 
oxide.  Unfortunately  neither  is  stab'le  in  the  presence  of  very  much  elec- 
trolyte, and  experiments  could  be  conducted  with  soils  which  had  been 
limed  not  to  exceed  a  ton  and  a  half  per  acre.  The  tests  failed  to  show 
any  differences  in  adsorptive  power.  In  other  words,  limes  do  not 
precipitate  hydrous  aluminum  oxide  when  added  in  the  equivalent  of  a 
ton  and  a  half  per  acre.  The  writer  has  found  eosin  to  be  much  better 
than  either  of  the  above  dyes  for  the  study  of  the  adsorptive  power  of 
aluminum.  Its  adsorptive  equilibrium  is  not  influenced  by  salts  present 
in  solution  in  the  equivalent  of  10  tons  per  acre. 

ADSORPTION  OF  EOSIN  BY  SOILS  TREATED  FOR  45  DAYS 


Treatment 

Ca(OH)2 

L.  S. 

p.  CaCO3 

(Jypsum 

Na2C03 

Checks 

\y2  T. 

56 

58 

51 

45 

54 

54 

10  T  

45 

45 

40 

41 

48 

ADSORPTION  OF  EOSIN  BY  SOILS  TREATED  FOR  225  DAYS 


Treatment 

Ca(OH)2 

L.  S. 

p.  CaCO3 

Gypsum 

Na2C03 

Checks 

\y2  T 

26 

25 

94 

25 

22 

30 

10  T  

24 

24 

24 

25 

23 

It  seems  from  the  above  data  that  all  limes  precipitate  aluminum  to 
some  degree.  Probably  gypsum  has  a  stronger  action  in  this  respect 
than  any  of  the  others. 

Taking  the  adsorption  data  as  a  whole,  it  appears  that  the  primary 
effect  of  liming  is  the  precipitation  of  the  silicic  acid,  as  indicated  by  the 
methylene  blue  tests.  The  influence  of  lime  is  noticeable,  even  when 
added  in  very  small  amounts.  Indirectly,  we  also  get  a  precipitation 
of  the  aluminum,  and  perhaps  the  organic  matter.  Any  statement  as  to 
the  effect  on  the  colloidal  iron  will  have  to  be  deferred  until  a  suitable 
dye  is  obtained. 


THE     PHYSICAL    ACTION     OF     LIME     ON     CLAY     SOILS 


23 


HYGRO-INTERSTITIAL  MOISTURE   STUDIES 

In  view  of  the  unsatisfactory  results  obtained  by  the  Rodewald-Mit- 
scherlich  method,  it  seemed  desirable  to  revert  to  the  type  of  procedure 
used  in  the  beginning.  The  writer  has  been  fortunate  in  obtaining  a 
method  which  is  free  from  errors  due  to  condensation,  and  is  at  the  same 
time  exceedingly  accurate.  Preliminary  work  with  this  method  indicates 
that  liming  seems  to  have  no  significant  effect  on  hygro-interstitial  mois- 
ture in  amounts  equivalent  to  the  lime  requirements  of  the  soil.  Exces- 
sive applications  decrease  the  value. 

OXIDATION  STUDIES. 

The  work  was  conducted  as  follows :  The  equivalents  of  four  grams  of 
soil  were  weighed  into  8-oz.  bottles,  and  50  cc.  of  phenolphthalein  solu- 
tion added.  After  oxidation  had  progressed  satisfactorily,  the  solutions 
were  cleared  of  humus  and  suspended  matter  with  hot  alum  solution,  an 
aliquot  made  alkaline  with  ammonia,  and  read  against  a  standard.  The 
results  are  as  follows:  (Each  figure  is  the  average  of  three  determina- 
tions. The  probable  error  is  approximately  a  plus  or  minus  two). 

OXIDATION  OF  PHENOLPHTHALEIN  BY  SOILS  TREATED  FOR  100  DAYS 


Treatment 

Check 

Ca(OH)r 

L.  S. 

p.CaCOs 

p.  CaSO4 

Na2CO3 

3.  MgCO3 

Yi  T. 

75 

97 

87 

100 

76 

95 

82 

IV?  T.. 

88 

72 

98 

.58 

95 

71 

10  T 

104 

63 

71 

50 

86 

47 

OXIDATION  OF  PHENOLPHTHALEIN  BY  SOILS  TREATED  FOR  225  DAYS 


Treatment 

Checks 

Ca(OH)2 

L.  S. 

p.  CaCO3 

Gypsum 

Na2CO3 

y2  T. 

71 

62 

63 

46 

61 

iy2T  

10  T  

76 

82 
88 

72 
75 

72 
73 

45 

57 

53 
52 

The  data  for  the  soil  run  225  days  goes  just  about  as  we  would  like  it 
to  go.  We  get  the  greater  oxidation  in  soils  in  which  we  would  expect 
the  greater  internal  surface,  and  we  obtain  a  decrease  in  oxidation  with 
increasing  applications  of  lime.  The  results  for  the  soils  run  100  days 
are  not  quite  so  satisfactory.  It  may  be  that  in  certain  cases  an  exchange 
of  bases  results  in  the  release  of  substances  which  catalyze  the  reaction. 


24  THE     PHYSICAL     ACTION     OF     LIME     ON     CLAY     SOILS 

STUDIES  WITH  PLAT  SOILS 

An  attempt  was  made  to  determine  whether  differences  could  be 
observed  between  soils  from  limed  and  unlimed  plats,  using  our  methods 
for  estimating  internal  surface.  Accurate  samples  of  the  surface  and 
subsoil  were  taken  from  plats  7007,  7008,  7207,  7208,  3611,  3612,  3613, 
and  3614.  The  seven  thousand  plats  received  a  moderate  application  of 
CaO  in  the  summer  of  1915,  while  the  three  thousand  plats  were  last 
limed  in  the  summer  of  1910.  The  soils  were  examined  according  to  the 
total  retentive  power,  dye  adsorption,  and  oxidation  methods.  None  of 
the  results  were  consistent  with  regard  to  the  limed  and  unlimed  plats, — 
with  one  exception, — the  oxidation  results  for  the  seven  thousand  plats. 

OXIDATION  OF  PHENOLPHTHALEIN  BY  LIME  PLAT  SOILS 


Soil 

Description 

Comparative  Figure 

7007  .  . 
7008  
7237  

rnlim;-d  
lirru  d  

r<).r, 

63  0 
93.0 

720*  

Limed  

106.0 

The  above  figures  are  averages  of  duplicate  determinations,  and  the 
probable  error  is  less  than  one.  W<-  may  conclude  that  several  years  time 
are  usually  sufficient  to  virtually  obliterate  all  physical  differences 
between  limed  and  unlimed  soils. 

DISCUSSION 

Six  methods  have  been  employed  in  the  present  investigation.  \Vc 
have  observed  that  the  total  retentive  power  and  penetration  procedures 
are  not  particularly  valuable  because  of  the  hi^h  probable  error  involved. 
The  oxidation  method  has  not  been  used  sufficiently  as  a  means  of  esti- 
mating internal  surface  to  permit  its  appraisement  at  the  present  time. 
Expansion,  hygro-interstitial  moisture,  and  dye  adsorption  seem  to  be 
accurate  and  valuable  methods.  It  appears  to  the  writer  that  the  dye 
method  has  the  brightest  future  of  all,  for  it  permits  the  determination 
of  tlie  effect  of  substances  in  specific  materials. 

CONCLUSIONS 

1.  The  penetration  method  is  not  a  suitable  procedure  for  estimating 
internal  surface. 

2.  Small  contraction  exhibited  by  a  salt  treated  soil  does  not  neces- 
sarily imply  large  expansion. 

3.  Gypsum  treated  soils  contracted  less  than  any  other  lime  treat- 
ment. 


THE     PHYSICAL     ACTION     OF     LIME     ON     CLAY     SOILS  25 

4.  Gypsum  appears  to  be  an  active  precipitant  of  silicic  acid  and 
hydrous  aluminum  oxide. 

5.  New  methods  for  the  determination  of  soil  expansions  and  hygro- 
interstitial  water  have  been  devised. 

6.  Liming  in  amounts  equivalent  to  the  lime  requirement  of  the  soil 
has  no  effect  on  the  hygro-interstitial  water. 

7.  Calcium  hydrate  is  only  slightly  more  valuable  as  an  ameliorating 
agent  than  limestone. 

s.     The  physical  effect  of  precipitated  magnesium  carbonate  on  the 
soil  is  nil. 

9.  The  dye  adsorption  method  has  the  greatest   possibilities  of   all 
methods  for  estimating  internal  surface. 

10.  The  primary  effect  of  liming  is  on  the  silicic  acid. 

• 
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